Explosive projector for projectiles



06f. 8, 1968 A, G, BLE-K 3,404,60@

EXPLOSIVE PROJECTOR FOR PROJECTILES Filed Sept. 20. 1966 INVENTOR. vaefw zu fr g4/QW ABSTRACT OF THE DISCLOSURE An explosive projector for propelling projectiles and in Which the casingcontainingn the high explosiveis closed at the forward end by a wax plate having embedded therein one or more projectiles. The plate is provided with a re-entrant cone extending into the high explosive. Thus, the high explosive has a shaped charge where it abuts the cone. There is also a disc of laminated Fiberglas transverse of the casing and embedded in the high explosive, the disc being positioned closer to the paraffin closure end of the casing than the other end to change the shape of the shock wave at the position of the disc. Greater focusing elect of the explosive at the shaped charge surface of the high explosive and against the projectile is thereby obtained. The wax, upon vaporization, serves to prevent damage to the projectile by providing a gaseous envel-ope about the same and also increases the velocity of the projectile through jet action of the vapor stream.

The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon. l

The presentinvention relates to an explosive projector, more particularly for propelling projectiles `at hypervelocities, either down an instrumented ballistic range or against a target.

AIt is known that when a projectile is propelled by a detonated high explosive, the force of the explosion and resulting shock wave tend to damage the projectile. In some instances, the shock is so gre-at as to destroy the projectile.

An object of the invention is t-o directionally propel a single or mul-tiple projectile array down an instrumented ballistic range or against a target with an absolute minimum of projectile 'breakup on tiring.

Another object of the invention is to propel a projectile or a number of projectiles at a hypervelocity when using a shaped charge of an explosive propellant and without damage to the projectile.

Still `another object is to impart to a projectile the highest possible velocity for a given charge of explosive material and to vary the velocity when desired without changing the amount of explosive charge.

A more specific object is -to control the det-onation front f a projectile propelling explosion by the use of a shock decoupling or consuming material which, upon vaporization, forms a jet to increase the velocity of the projectile. The material `thus serves to soften the eliect of the shock wave front on the projectile as well as imparting greater velocity thereto. y These objects are attained in brief by focusing the wave front onto a body of vaporiza-ble material such as paratiin or other wax `and causing the latter to gasify as a fast-moving jet which Iaccelerates the projectile to an ultrahigh velocity, while protecting the latter from damage due to the impact of wave front.

The invention will be better understood when reference is made to the following description in connection with the accompanying drawings, in which:

FIG. 1 represents an explosive shell partly broken away United States Patent O ice and in section, containing a single projectile to show the principle of my invention;

FIG. 2 is a view similar to FIG. 1 but showing the shock front as a line pattern formed at the instant of detonation of the explosive charge but prior to the completion of the explosion; and

FIG. 3 illustrates the application of the invention to a modified form of the improved explosive shell which accommodates more than one projectile.

In FIG. 1, reference character 1 refers to a shell or casing, preferably cylindrical, and containing a high-explo- .sive material 2 such.as trinitrotoluene (TNT). The cylinder may be constituted of thin Fiberglas and is closed at the left-hand end except for an opening (not shown) which receives a small cylinder 3 containing a booster charge of any and suitable well-known type. A blasting cap 4, or other form of detonator, also well known in the art may be employed to set ofi the booster charge. The right-hand end of the cylinder is closed by a plate 5 provided with an inwardly extending cone 6, the apex of which preferably subtends at an angle of about 90. The member 5 and its cone projection may be constituted of a material such as paraflin or other wax which readily liquelies and changes instantly to gas or vapor when subjected to an explosive shock and the accompanying heat. A projectile 7 of any desired type is encased in the wax directly in line with the axis of the cone. The projectile may be constituted of Ia cylindrical body, preferably rounded at `the end nearer the cone but iiat at the other end, as illustrated, or may comprise a right circular cylinder, a sphere or even a rodlike member. The plate 5 and cone of wax serves as a shock decoupling material which forms a gaseous jet as will be explained presently.

Within the explosive material there is embedded a socalled wave reversing element in the form of a disc 8 made of laminated Fiberglas and having a diameter of possibly 11/2" and about 1%2 thick. In this case, the shell or casing may have a 4diameter of about 21/2. The disc is positioned transversely of the axis of the cylinder and about 1%" from the inside iiat surface of the wax plate 5. It will be understood that the dimensions of the various parts and positions set forth are purely typical and may be changed considerably depending on a number of factors including the size of the casing, the size and number of the projectiles to be propelled, also the velocity to be imparted to the projectile or projectiles.

When an explosive charge is initiated by the detonator, an intense shock wave would norm-ally travel at hypervelocity through the casing or shell. The shock wave would strike the stationary projectile with such force, in imparting velocity thereto, as might damage or even completely destroy the member. Furthermore, the strength of the shock and accompanying damage would be enhanced should the high explosive be present in the form of a shaped charge. In this connection, it will be understood that a shaped charge serves to concentrate or focus the Iblast against the object toward which it is directed by the configuration of the charge.

Reference should now be made to FIG. 2 which shows the forces caused by the high explosive, i.e., the shock front, as it travels along the casing. In the figure, this moving front is indicated by a series of dash lines 9, which as noted, follow large circular arcs concave with respect to the disc 8 on the left-hand side thereof and convex on the reverse side of the disc. Thus the disc serves as a wave-shaping element in reversing the detonation front. The reason for this reversal of the shock front is the fact that the shock or dilational velocity through the laminated element is considerably less than the detonation rate so that the unimpeded portion of the explosion wave, indicated at 9, progressing normally along the surface of 3 A f the cylinder, i.e., beyond the periphery of the disc, is ahead of the central region indicated by the area marked 10. Consequently, the wave front is effectively reversed and this front now begins to converge on the central portion of the paraffin including the cone 6. This directing effect of the front is identified by the arrows 11. Since there is an effective time lag in the pressure exerted on the apex of the outer region of the cone beyond the apex, the converging effect of the detonation front causes the paraffin instantaneously to melt and form a centrally located gaseous jet which accelerates the projectile 7 to an ultrahigh velocity. The projectile is not damaged for the reason that the dilational or shock velocity through the paraffin or wax is so low as to damp the brisance of the detonation Wave. Another reason is that the paraffin or other wax, underthe influence of the intense compress-ion forces acting on it, rapidly changes from a solid to a liquid to a gaseous state. In changing from a solid to a liquid, some additional energy absorption and cushioning effect is provided. As the projectile begins to accelerate, the paraffin or other wax ignites and forms a gaseous envelope about the projectile which further protects the latter from the intense pressures developed at the detonation front. At this point, the projectile is imparted with a velocity which is not less than one-half the detonation rate and this is a much greater velocity than has heretofore been obtainable. Having given up much of its accelerating force through the jet action of the vapor stream, the detonation front becomes greatly weakened and passes harmlessly over the projectile.

The paraffin or waxes are completely consumed (burned) in the process, thus permitting free propulsion of the projectile and the latter remains uncluttered by accompanying debris. This might be important in case the explosive projector is utilized in connection with ballistic impact studies.

It is apparent that the projectile 7 should preferably be so positioned as to be axially in line with the jet produced by the gasified parafhn. Its velocity is dependent upon its relative position with respect to the converging or focusing point of the detonation wave. When the position of the projectile is in sharp focus, the imparted velocity is highest. Conversely, as the projectile-launch position departs from the preferred position mentioned, the imparted velocity is gradually reduced in some proportion to the distance. In this way, the projectile velocity can be varied.

FIG. 3 shows a projectile-launching structure similar to FIGS. 1 and 2, except as applied to a multiplicity of projectiles. Similar reference characters are used in FIG. 3 to designate corresponding elements described in FIG. 1 and therefore need no further description.

In FIG. 3, the projectiles 11 (typified as seven in number) are embedded in a mass of paraffin 12 or other Wax which closes the right-hand end of the cylinder 1. The wax body abuts the re-entrant surface of a shaped charge of high-explosive material 14. The latter fills the casing 1. The end of the shaped charge where it abuts the paraffin mass 12, has a conically-shaped recess 15, preferably in line with the axis of the center row of the projectiles in order to maintain symmetry as far as possible. This recess is provided with a typical liner 16 of any suitable and well-known material having a circular angle of about 90 and snugly fitting into the recess. This liner assists in focusing the shock front onto the projectiles.

'I'he outer end of the charge, and therefore the inner boundary of the paraffin mass, preferably has a reverse curvature indicated at 17. The directions in which the force of the explosion is manifested is roughly shown by the arrows 18. The disc 8, as in the case of FIG. 1, serves to slow downthe shock Wave in the center region but allows the shock front to travel unimpeded around the periphery of the disc with the result that the shape of the shock wave is concave on the left-hand side of the disc but convex on the opposite side. The disc therefore again serves as a shock wave reversing member to cause a strong concentration or focusing effect on the central port-ion of the paraffin body where the projectiles 11 are located.

As explained hereinbefore, when the charge 14 is exploded by the igniter cap, and a booster employed if necessary, the traveling shock wave indicated by the dotted line pattern travels from left to right and the shaped charge end 15, including the liner 16, directs this shock wave toward the axis of the cylinder. The body of paraffin 12 passes through the liquid to the gaseous state to form a fast-moving jet which propels the projectiles toward the target or down the instrumented ballistic range. The jet also provides each projectile with a protective vaporous covering against damage by any portion of the shock front which may overtake the projectile or projectiles.

While I have shown and described the structures of FIGS. 1 and 3 as including the wave-reversing member 8 for providing a focused shock front as it approaches the paraffin closures 5, 12 and the embedded projectile, it will be understood that even in the absence of such member 8, the shock wave might still cause the paraffin to form a jet. The latter would propel the projectile and offer some protection from damage. In this case, a certain amount of directing effort on the shock wave would also be present on account of the shaped charge effect offered by the right-hand end of the high-explosive material. However, the speed of the ejected projectile would be considerably less than if the member 8 were employed on account of the less obtainable focusing effect that would have been available through the use of the disc. It is apparent that the latter could take various shapes, such as concave or convex and different sizes and thicknesses in order to obtain any desired degree of reversal of the shock front as a portion thereof travels from one side of the disc, around the edge thereof, to the other side. It has also been pointed out that the speed of the projectile can be controlled by Varying its position within the mass of parafiin and also with respect to an imaginary axis that passes through the apex of the liner or of the cavity of the explosive material.

From the foregoing, it is evident that I have disclosed not only a unique structure for imparting hypervelocty to a projectile or projectiles, by the use of paraffin or other wax transformed to a fast-moving jet by the use of a high explosive, together with providing protection to the projectile from the overtaking detonation front, but have also shown the manner in which the speed of the projectile can be varied when and if desired.

While a certain specific embodiment has been described, 1t is obvious that numerous changes may be made without ldeparting from the general principles and scope of the invention.

I claim:

1 An explosive projector for propelling projectiles, said projector comprising a casing c-ontaining high-explosive material, said casing being closed at one end except for an explosion-initiating device, the other end of the cas- 1ng being completely spanned by a paraffin plate member containing a projectile, said plate member abutting the end of the explosive material, and means for causing the configuration of the shock wave as it travels along the casing toward the parafiin plate member when the explos1on is initiated to Vassume a focusing effect on said member in the region of the projectile, said means comprising a fiat disc positioned transversely of the casing embedded in the explosive material, said disc being of smaller size than the casing to permit a portion of the shock wave to pass unimpeded between the edge of the disc and the casing but to permit retardation of the central portion of the shock wave which passes through the disc.

2. An explosive projector for propelling projectiles, said projector comprising a casing containing high-explosive material, said casing being closed at one end except for an explosion-initiating device, the `other end of the casing being completely spanned by a parafn plate member containing a projectile, said plate member abutting the end of the explosive material, and means for causing the configuration of the shock wave as it travels along the casing toward the paran plate member when the explosion is initiated to assume a focusing effect on said member in the region of the projectile, said last-mentioned means being constituted of a thin, circular member of laminated Fiberglas positioned transversely of the cylinder but of small diameter and arranged concentrically on the axis of the cylinder to divide the shock wave into portions which have different rates of speed through the cylinder to change at least a portion of the shock front from a concave to a convex configuration and thus pro- 15 vide a focusing effect on the paraffin member and contained projectile.

References Cited SAMUEL W. ENGLE, Primary Examiner. 

